This invention relates to instruments for taking measurements from wells and boreholes, being measurements of such parameters as water level, water pressure, temperature, and the like. The invention relates particularly to a system for configuring the various sensors, and for co-ordinating and presenting the data emanating therefrom.
The task of gathering data from water wells and boreholes, and from bodies of water generally, has been the subject of much attention. However, the instruments and associated apparatus available hitherto have been somewhat inconvenient, especially from the standpoint of versatility and operational flexibility, and as to the presentation of the data obtained from the boreholes. The invention provides a modular system, which is aimed at easing some of these shortcomings.
Generally, the data from sensors, probes, and other instruments in water wells and boreholes is intended to be fed into a computer for final storage and presentation. The data may be transferred from the field equipment (i.e the equipment located actually at the well) to the computer by wire, by radio channel, via an infra-red data-communication port of the computer, or as appropriate. Instructions for operating the data gathering equipment can be communicated in the same way.
The invention has a two-wire cable going from the surface unit to the down-hole unit. This cable physically supports the down hole string of modules, the cable being capable of supporting not only its own weight and the weight of the string of modules, but also of enabling the cable to be tugged and pulled from the surface if the string should become snagged in the borehole.
The cable includes just two electrical conductors on the cable, and between the modules. One conductor is passed from module to module via the insulated central electrodes, and the other is passed via the module casings.
One of the main bases for the design of the present apparatus is to avoid the need for batteries on board the modules.
The modules include microprocessors, for conditioning and transmitting the data from the sensor to the surface. The microprocessor is mounted on a circuit board in the module, to which electrical leads connect the electrodes and the casing, and the sensor.
The sensors are for sensing down-borehole parameters, such as temperature, pressure, salinity, pH, oxygen-content, and so on.
The data from the different modules is multiplex-transmitted via the two-wire cable. The multiplexing system may be of the random-access type, with each module being uniquely addressable, or of the time-division type, with the modules being addressable only sequentially.
The system as described is aimed at ensuring that a data-gathering from all the modules takes place in a minimum time. This is important for keeping overall energy-draw from the battery to a minimum.